While reductions in dental decay have been dramatic in many children and young adults in the US, caries remains a major disease in adults and particularly in special groups of children in our population and many developing countries where dental decay is increasing rapidly. Reasons why these persons do not enjoy optimal anticaries benefits vary, but include lack of access to fluoridated water and/or topical F agents, and problems with compliance which may be related to physical and/or mental handicaps. Currently, an innovative delivery system, the fluoride-- releasing device (FRD), has been designed to provide significantly elevated salivary F levels for prolonged periods. As a topical agent, its effects upon caries prevention have not been tested. It is the purpose of this project to study the effects of the FRDs at two different release rates: (0.2mg and 1.0 mgF/day) upon the remineralization of early enamel lesions in vivo. Equal numbers of female (20) and male (20) subjects will be recruited to wear enamel specimens with subsurface lesions bonded to buccal surfaces of mandibular premolars and molars, and the FRDs bonded directly to the buccal surfaces of the maxillary first molars for a 90 day control and four 90 day test periods: 1) 0.2mg FRD, 2) 1.Omg FRD, 3) NaF dentifrice brushed 2X/day, and 4) 1.Omg FRD plus NaF dentifrice 2X/day. Half of each lesion will be covered with resin during intraoral exposure to allow measurement of changes in lesion parameters during treatment. A control and two FRD groups will use a free dentifrice, while a fourth group will use only a NaF dentifrice for comparison of FRD groups to a conventional topical regimen. The fifth group is included to demonstrate the additive benefits of FRD and NaF dentifrice used together. Saliva samples will be collected every two weeks for all periods and 4X during the first week for FRDs to test for the early surge in release of F reported by Corpron, et al. (1986). Salivary flow rates and F levels will be measured for both resting and stimulated saliva samples. Levels of remineralization will be assessed by measuring changes in mineral density using microradiography and F uptake on the same -enamel section using secondary ion mass spectrometry (SIMS) on identical areas of the same section of untreated and control or treated lesions. This method allows direct correlation of changes in mineral density to F uptake. Saliva flow rates and F levels will be compared to levels of remineralization. Sex differences and intersubject differences in salivary flow rates, F levels in saliva, and levels of remineralization will be examined.